The present invention provides a method of directly converting ring unsaturated prostaglandins of the 15-epi PGA.sub.2 and PGA.sub.2 type, that is, 7-(2-[(3R and 3S)-3-hydroxy-1-octenyl]-5-oxo-3-cyclopenten-1-yl)-5-heptenoic acids, to 11-deoxy-15-epi- and 11-deoxy-PGE.sub.2, respectively.